When a storage apparatus accumulates data, in order to reduce the data amount, the storage apparatus deletes duplicate data. However, in order to accurately manage the duplicate number of data, upon updating of the data, such processes as reading out of existing data, decrease the duplicate number of the read out data by one, writing of new data, and increase of the duplicate number of the new data by one are performed. Therefore, the updating process of data is delayed.
A related technology is disclosed in Japanese Laid-open Patent Publication No. 2014-199573 or Japanese National Publication of International Patent Application No. 2013-514560.